1. Technical Field of the Invention
The present invention relates to telecommunication systems and, more particularly, to systems and methods for providing wireless telephony over a packet-switched network such as, for example, a network using the Internet Protocol (IP).
2. Description of Related Art
Coupled with the phenomenal growth in popularity of the Internet, there has been a tremendous interest in using packet-switched network (PSN) infrastructures (e.g., those based on IP addressing) as a replacement for the existing circuit-switched network (CSN) infrastructures used in today""s telephony. From the network operators"" perspective, the inherent traffic aggregation in packet-switched infrastructures allows for a reduction in the cost of transmission and the infrastructure cost per end-user. Ultimately, such cost reductions enable the network operators to pass on the concomitant cost savings to the end-users.
The existing Voice-over-IP (VoIP) networks implement communications infrastructures that are typically based on multiple protocols which include, for example, the well-known H.323 protocol. These protocols are primarily oriented to operating with fixed-network-based telecommunications protocols and are designed to provide such services as call control, et cetera, for wireline subscribers only. Current VoIP systems, accordingly, cannot be used advantageously in wireless environments, although some VoIP systems may support rudimentary location management services.
There also exist several inadequacies in the Plain Old Cellular System (POCS) with respect to supporting IP-based infrastructures and services. Also, there exist deficiencies and shortcomings in the existing IP-based VoIP systems in terms of supporting wireless access technology such as for example, ANSI-136, Global System for Mobile communications (GSM), IS-95, et cetera. Some of the more significant of these inadequacies and shortcomings are summarized below.
First, current POCS systems and technology infrastructures are not compatible with communications infrastructures as required by the VoIP standards. The operation, maintenance, and the connection management required by the traditional POCS systems are based on switched physical trunk connections. These mechanisms are not compatible with the packet switching/routing mechanisms such as, e.g., Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP), etc. required for managing device/host addressing and configuration.
Incompatibilities also exist between POCS protocols and communications protocols of the existing VoIP applications. The POCS systems cannot support a Plain Old Telephone System (POTS) or Integrated Services Digital Network (ISDN) client in the Internet context. The Internet xe2x80x9cclientxe2x80x9d is typically required to handle Internet-based protocols such as, e.g., Real-time Transfer Protocol (RTP), Resource Reservation Protocol (RSVP), etc. which are not in the definition or domain of the POCS systems.
Another important disparity which should be noted is that the POCS signaling and user data planes use distinct physical transport and network facilities. The IP-based networks are flexible in that they can support any higher layer protocols, and information can be transmitted over any lower layer e.g., a link or physical layer. Moreover, the higher layer protocols may be used for signaling as well as user data.
With respect to the inadequacies of the existing VoIP systems, it should be appreciated that current VoIP clients and infrastructure can handle neither the wireless access-side technology nor the basic network-side functional signaling plane which enables mobility management, authentication/security, service definition, service mitigation and execution, et cetera. Clearly, the provision of such advancements in the POCS as Wireless Intelligent Network (WIN) services, can only magnify these and other disparities and incompatibilities between the POCS and VoIP infrastructures.
Based on the foregoing, it is apparent that in order to address these and other problems of the current technologies set forth above, what is needed is a seamless integration between the existing POCS and VoIP infrastructures so that the numerous advantages, known and hitherto unknown, of packet-based networks may be realized within the context of wireless telecommunications. The present invention provides such a solution.
In exemplary embodiment, the present invention advantageously integrates the existing VoIP packet switching infrastructures with the POCS by selectively replacing structural and functional elements that allow the existing VoIP and POCS systems to co-exist and evolve independently. In other words, legacy infrastructures in each realm are left intact to the extent possible in order to provide backward compatibility. Accordingly, in the presently preferred exemplary embodiment of the present invention, available VoIP functions are substituted for corresponding ANSI-136/41 functions, while the remaining ANSI-136 functions preferably continue to exist in their legacy form. To minimize infrastructure modifications, a mechanism is introduced for interfacing the xe2x80x9cfootprintxe2x80x9d of a VoIP system with the POCS legacy structures with respect to call control, mobility management, subscriber services, et cetera.
Accordingly, a presently preferred exemplary embodiment is directed to an integrated network system comprising a packet-switched network portion and a cellular telecommunications network portion, with an interworking function module (or proxy device) disposed therebetween for interfacing between the legacy POCS and VoIP PSN infrastructures. The proxy device is preferably comprised of a xe2x80x9cVoIP proxyxe2x80x9d or xe2x80x9cIP clientxe2x80x9d and a mobility gateway (MGW or Mob.GW). The MGW preferably handles signaling information between the POCS CSN and PSN infrastructures. The proxy/IP client, on the other hand, handles IP traffic (signaling and user data, which includes voice or other information) therebetween for mobility management, security and subscriber services, respectively. Accordingly, the proxy makes, or provides, the link between, on the one hand, the POCS legacy mobility, security, subscriber services and supplementary WIN services, and on the other hand, the VoIP PSN-specific legacy mobility management, security and services, regardless of whether these are interfaced from the IP client, or the server disposed in the VoIP infrastructure.
The MGW""s role is preferably to xe2x80x9cgatexe2x80x9d the transfer of control signaling information relating to the aforementioned functions. In accordance with the teachings herein, the functionality of a presently preferred exemplary embodiment of the Mob. GW (or MGW) is summarized below.
A Mob. GW implements the mobility management entity that maintains the MS-associated VoIP infrastructures"" location information. The Mob. GW handles the ANSI-41 automatic roaming signaling interface for location management towards the ANSI-41 (a subset of the D interface). In this sense, it is seen as a Visitor Location Register (VLR) by the ANSI-41 PLMN. It also implements the PSN-specific location management signaling interface to and from the PSN infrastructure (e.g., RAS, SIP signaling etc.). Hence, the Mob. GW is also a protocol converter between the ANSI-41 and H.323/SIP signaling.
The Mob. GW also handles the call routing interface between the ANSI-41 PLMN and PSN VoIP networks. This mechanism enables (i) the routing of a call and/or service from the PSN towards the associated ANSI-41 PLMN portion; and (ii) the routing of a call and/or service from the ANSI-41 PLMN portion towards the served PSN VoIP system. Thus, the Mob. GW handles the part of the ANSI-41 automatic roaming signaling interface for call delivery (e.g., location requests, route requests, etc.) towards the ANSI-41 PLMN. On the PSN side, the Mob. GW implements the H.323 or SIP call routing interface.
In one exemplary embodiment, the proxy device or its constituents (i.e., Mobility GW, various IP clients, etc.) may be implemented as co-located components within cellular infrastructures. For example, the MGW functionality can be advantageously provided within a VLR. Also, the MGW may be realized as a distinct intermediary entity provided between (i) the IP client functions and the ANSI-41 network, and (ii) the IP server functions and the ANSI-41 network. One of ordinary skill in the art should understand that the MGW may also be provided closer to the POCS infrastructures so as to realize savings in transmission. In either embodiment, the device is responsible for routing the ANSI-41 signaling and H.323/SIP signaling for location management and security purposes (registration from the PSN side), for call routing (ANSI-41 location request and route request messages), and finally for service handling (service triggering, mitigation and execution) purposes.
In one broad aspect, therefore, the preferred embodiment of the present invention advantageously provides an integrated telecommunications network comprising a cellular network portion which provides legacy mobile telecommunications functionality to mobile subscribers and a packet-switched network (PSN) portion for transporting communication traffic. The communication traffic comprises traffic originated from a mobile subscriber, traffic intended for a mobile subscriber, or both. The network also includes a gateway, e.g., media gateway, disposed between the cellular network portion and the packet-switched network portion for providing a communication path therebetween. An interworking interface module is provided between the cellular network portion and the PSN portion. The interworking interface module preferably comprises a mobility gateway and an Internet Protocol (IP) client, wherein the mobility gateway handles mobility management information and the translation of control signaling information between the cellular network portion and the PSN portion. The IP client handles communication traffic with one or more associated servers provided in the PSN portion with respect to, e.g., mobility management, security, and subscriber services of the mobile subscriber.
In an alternative embodiment, the present invention is directed to an integrated wireless VoIP network which includes a cellular portion and an IP portion. The integrated wireless VoIP network comprises a Mobile Switching Center (MSC) serving a mobile terminal located in the MSC""s serving area and a gateway (e.g., media gateway) located nearest to the serving MSC. The gateway is included for providing a communication path between the cellular portion and the IP portion. A Visitor Location Register (VLR) is associated with the MSC for maintaining location information with respect to the mobile terminal registered thereat. Preferably, the location information stored at the VLR includes the location of the nearest gateway. A gatekeeper is included in the integrated wireless VoIP network for providing location inquiry messages in response to a call placed by a calling party, wherein the call is intended for the mobile terminal. Further, an interface device is advantageously disposed between the VLR and the gatekeeper. When the location inquiry messages are sent out by the gatekeeper, the interface device translates the messages received thereat into messages compatible with the VLR so that the gateway location information with respect the registered mobile terminal is returned to the gatekeeper for call routing. In alternative embodiment, the interface device may be directly coupled to the IP portion via a connection path for transporting the location inquiry messages.
In a further aspect of the alternative integrated network embodiment, the present invention provides a method of routing a calling party""s call to a mobile terminal in an integrated wireless packet-switched network which includes a cellular network portion and a packet-switched network portion. The cellular network portion comprises a VLR having an interface operable with the packet-switched network portion. An MSC is provided for serving the mobile terminal when located in the MSC""s serving area. The packet-switched network portion is coupled to a gatekeeper and a gateway that is located closest to the MSC. The call routing method begins when the call intended for the mobile terminal is received in the packet-switched network portion. Responsive to the call, a request message is sent from the packet-switched network portion to the gatekeeper for locating the mobile terminal. In response, the gatekeeper sends a location request to the VLR interface for determining the address of the gateway that is located closest to the MSC. If the mobile terminal is registered at the VLR, a location confirm return message is sent therefrom to the gatekeeper. The return message includes the address of the gateway that is nearest to the MSC. Thereafter, the call is routed to the gateway based on the received address.
In a further aspect of an alternative embodiment, the present invention is directed to a method of routing a calling party""s call to a mobile terminal in an integrated wireless packet-switched network system which includes a cellular network portion and a packet-switched network portion. The cellular network portion preferably comprises a Home Location Register (HLR) having an interface operable with the packet-switched network portion and an MSC visited by the mobile terminal. The packet-switched network portion preferably comprises a gatekeeper and a gateway, wherein the gateway is located closest to the VMSC. The method begins by receiving the call in the packet-switched network portion, wherein the call is intended for the mobile terminal served by the VMSC. Responsive to the call, an admission request message is sent to the gatekeeper for locating the mobile terminal. Responsive to the admission request message, a location request is issued to the HLR interface for determining the address of the gateway that is located closest to the VMSC. A location confirm return message is sent from the HLR interface, with the gateway""s address included therein. Thereafter, an admission confirm return message is sent from the gatekeeper to the calling party. Subsequently, the incoming call is routed to the gateway based on the received address from the gatekeeper.
The present invention, in a further aspect, is directed to several presently preferred exemplary embodiments of a call handoff method usable in the alternative network embodiment. In a first embodiment, an inter-MSC call handoff method is provided for handing over a call between a mobile terminal and a party in an integrated wireless packet-switched network system. First, second and third gateways, and one or more gatekeepers associated therewith are disposed within the integrated wireless packet-switched network system, wherein the first gateway is coupled to a first MSC, the second gateway is coupled to a second MSC, and the third gateway is associated with the party. The initial call path involves the first MSC, and the first and third gateways over the packet-switched network portion. The call handoff method commences by sending a handoff measurement request from the first MSC to the second MSC. The first MSC then receives a handoff measurement response message from the second MSC. Responsive thereto, a facility directive message is sent from the first MSC to the second MSC. The first MSC then notifies the third gateway to set up a connection between the second and third gateways over the packet-switched network portion. Accordingly, the connection between the second and third gateways is set up over the packet-switched network portion. Thereafter, a handoff order is sent from the first MSC to the mobile terminal, and the initial call path is released once the mobile terminal is received by the second MSC on a designated channel.
In a second embodiment, an inter-IP handoff method is provided for handing over a call between a mobile terminal and a party in an integrated wireless packet-switched network system. First and second gateways, and a serving gatekeeper associated therewith are disposed in the integrated wireless packet-switched network system, wherein the first gateway is coupled to an MSC and the second gateway is associated with the party. A software-defined radio base station (SDR BS), having direct IP-connectivity and controlled by a Mobile Switching Application (MSA), is directly connected to the packet-switched network portion. The initial call path involves the MSC and the first and second gateways over the packet-switched network portion. The call handoff method begins by sending a handoff measurement request from the MSC to the MSA. The MSC then receives a handoff measurement response message from the MSA. A facility directive message is then sent from the MSC to the MSA. Responsive thereto, a facility directive response message is sent from the MSA to the MSC. Subsequently, a handoff indication and an address of the software-defined radio base station are sent to the serving gatekeeper from the MSC. In response, a logical channel is established between the first gateway and the software-defined radio base station. The MSC is notified thereafter to issue a handoff order to the mobile terminal. The initial call path is released once the mobile terminal is received by the software-defined radio base station on a designated channel.
In a third exemplary embodiment, another inter-MSC call handoff method is provided for handing over a call between a mobile terminal and a party in an integrated wireless packet-switched network system using an intermediate call path which includes an inter-MSC trunk path between a first MSC and a second MSC for a selected period of time. The integrated wireless packet-switched network system includes first, second and third gateways, and one or more gatekeepers associated therewith, wherein the first gateway is coupled to the first MSC, the second gateway is coupled to the second MSC, and the third gateway is associated with the party. The initial call path involves the first MSC, and the first and third gateways over the packet-switched network portion. The call handoff method begins by sending a handoff measurement request from the first MSC to the second MSC. A handoff measurement response message from the second MSC is received in the first MSC. Responsive to the handoff measurement response message from the second MSC, a handoff message is sent from the first MSC to the second MSC. Subsequently, an intermediate call path is established between the mobile terminal and the party, the intermediate call path involving a trunk segment between the first and second MSCs. A call connection between the second and third gateways over the packet-switched network portion is then negotiated. Upon completing the connection between the second and third gateways, the trunk segment between the first and second MSCs is released.
In a still further aspect, the present invention is directed to several embodiments of call routing systems and methods in an integrated wireless packet-switched network system. In one embodiment, a call routing system is provided which includes a Gateway Mobile Switching Center (GMSC) and a visited Mobile Switching Center (VMSC), each of which is equipped with a gateway interfaced with a packet-switched network portion disposed therebetween. Also included are an HLR coupled to the GMSC and VMSC, and a gatekeeper coupled to the gateway associated with the GMSC. The VMSC includes means for determining whether the call is to be routed through the packet-switched network portion, in addition to means for returning a non-routable number. When an incoming call intended for the mobile terminal is received in the GMSC, a non-routable number is forwarded thereto by the VMSC. The non-routable number is translated in the gatekeeper to obtain an address for the gateway associated with the VMSC, the address being operable with the packet-switched network portion. The gateway address is then used for routing the incoming call over the packet-switched network portion.
In another embodiment, a call routing method is provided for routing an incoming call to a mobile terminal served by a VMSC in an integrated wireless packet-switched network system. A packet-switched network portion is disposed between a GMSC and the VMSC, each of which is provided with a gateway for the packet-switched network portion which includes a gatekeeper. The method begins by receiving the incoming call in the GMSC, and in response, sending a location request from the GMSC to an HLR associated with the mobile terminal. A routing request message is then sent from the HLR to the VMSC which assigns a non-routable number to the route request message based on the mobile terminal""s location. Thereafter, a routing request return result message is sent from the VMSC to the HLR, the routing request return result message including the non-routable number. A location request return result message, including the non-routable number, is sent from the HLR to the GMSC. A setup request is forwarded by the GMSC to the gatekeeper which translates the non-routable number to obtain an address for the gateway associated with the VMSC. The incoming call is then routed from the gateway associated with the GMSC to the VMSC over the packet-switched network portion using the address for the gateway associated with the VMSC.
In a still further embodiment, the present invention provides a method of routing an incoming call to a roaming mobile subscriber in an integrated wireless packet-switched network system which includes a packet-switched network portion disposed between a GMSC and a VMSC. Each of the GMSC and VMSC is provided with a gateway for the packet-switched network portion. The method begins by detecting, in the VMSC, that the mobile subscriber is roaming in a serving area associated with the VMSC. Then, a registration message is sent from the VMSC to an HLR of the mobile subscriber. Responsive to the registration message, the HLR returns a subscriber profile associated with the mobile subscriber, the subscriber profile including a parametric indication of whether the incoming call is to be delivered to the mobile subscriber over the packet-switched network portion. When the GMSC receives the incoming call intended for the mobile subscriber, it sends a location request to the HLR. In turn, a routing request message is sent from the HLR to the VMSC. The VMSC returns to the HLR an address assigned to the gateway interfacing with the packet-switched network portion, wherein the gateway is associated with the mobile subscriber. Subsequently, the HLR determines whether the parametric indication indicates that the incoming call is to be delivered to the mobile subscriber over the packet-switched network portion. If so, the address of the gateway associated with the mobile subscriber is provided to the GMSC. The incoming call is then routed from the GMSC to the mobile subscriber over the packet-switched network portion, using the address of the gateway.
In yet another embodiment, a method is provided for routing an incoming call to a mobile subscriber in an integrated wireless packet-switched network system by indicating that a GMSC is capable of routing the call over a packet-switched network portion disposed between the GMSC and a VMSC. Each of the GMSC and VMSC is provided with a gateway for the packet-switched network portion. The method commences by receiving, in the GMSC, the incoming call intended for the mobile subscriber located in a serving area associated with the VMSC. Responsive thereto, a location request is sent from the GMSC to the HLR, the location request including a parametric indication that the GMSC is capable of routing the incoming call over the packet-switched network portion. A routing request message from the HLR to the VMSC also includes the GMSC""s parametric indication. The VMSC then determines if it is capable of communicating with the GMSC over the packet-switched network portion. If so, an address of the gateway associated with the VMSC is provided to the GMSC. Thereafter, the incoming call is routed from the GMSC over the packet-switched network portion to the mobile subscriber, using the VMSC""s gateway address.